Ganesh Vs Moon

The moon once laughed, when he saw Ganesha riding on a rat. This is because
the moon found the idea of an elephant headed big god riding a tiny
rodent very funny. Ganesha did not enjoy the moon laughter and declared
that anyone who looked at the moon on the fourth day of the waxing moon
in the month of Bhadrapada; will suffer bad luck. This is why no one
looks at the moon on Ganesha chaturthi. (This Chaturthi festival time
is special & sacred to Ganesha).